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Background: Interscalene brachial plexus block is an effective regional anesthesia technique for shoulder surgeries. The superiority of the popular ultrasound-guided blocks over peripheral nerve stimulator-confirmed blocks remains unclear. In this study the efficacy of these different block techniques was compared. Methods: This prospective, randomized, clinical study included 109 patients (ASA grades I-III) who receive 20 mL 0.5% ropivacaine with ultrasound-guided blocks (U group), peripheral nerve stimulator-confirmed blocks (N group), or ultrasound-guided and peripheral nerve stimulator-confirmed blocks (dual guidance; NU group) for elective shoulder arthroscopy. Block onset time, duration, and effectiveness on the Lovett rating scale were assessed. Results: There was no statistically significant intergroup difference in duration of block performance, irrespective of the technique (P = 0.232). Onset time of complete warmth sensation loss (P < 0.001) and muscle strength abolition (P < 0.001) was significantly longer and mean Lovett rating scale score distribution was significantly higher in the N group than in the other groups (P < 0.001). These findings show a statistically significant correlation between the performance of the used block technique and the necessity of conversion to general anesthesia because of insufficient block in the N group (58.54%) than in the U (24.44%) and NU (19.57%) groups. Conclusions: Peripheral nerve stimulator-confirmed needle placement is not necessary to ensure effectiveness of ultrasound-guided blocks, which is expressed as a lack of necessity of conversion to general anesthesia. Nevertheless, the dual guidance technique is recommended to reduce the risk of complications and might be considered the regional anesthesia of choice for shoulder surgery.

The precision of IBPB by use of the dual guidance technique may reduce the rate of Horner's syndrome. The higher water concentration in the prevertebral spaces of younger patients may create better conditions for the diffusion of ropivacaine, which may result in a statistically significant higher HS rate.

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Background: Shoulder arthroscopic procedures impose a challenge to anaesthesiologists in terms of postoperative analgesia. Proper pain management after arthroscopic procedures improves patient satisfaction and facilitates early rehabilitation. Methods: We performed a randomized, prospective clinical study to assess the influence of anthropometric parameters and IBPB technique on the quality of postoperative analgesia. A total of 106 randomly selected patients of ASA I-III status scheduled for elective shoulder arthroscopy. Reasons for exclusion were neurological deficit in the upper arm, allergies to amide-type local anesthetics, coagulopathy, and pregnancy.The patients received 20 mL of 0.5% ropivacaine for an ultrasound-guided interscalene brachial plexus block (IBPB) (group U), peripheral nerve stimulation (PNS)-confirmed IBPB (group N), or ultrasound-guided, PNS-confirmed IBPB (dual guidance; group NU). Results: We observed that the three groups did not differ in mean time of sensory and motor block terminations. In individual cases in each group, sensory block lasted up to 890-990 minutes, providing satisfactory long lasting postoperative analgesia in patients receiving IBPB. We observed a negative correlation between body mass index and termination of motor block (P = 0.037, Pearson's correlation coefficient) and a positive correlation between age and termination of sensory block (P = 0.0314, Pearson's correlation coefficient) in group U compared to the other two groups. We found a positive correlation between male gender and termination of motor block (P = 0.0487, Pearson's correlation coefficient) in group N compared to the other two groups. Conclusion: In our study, patients received satisfactory analgesia in the postoperative period regardless of technique used, age, gender, or potentially uncommon anthropometry.

The aim of this study was to estimate spectral properties and propagation of the EEG signals registered during sevoflurane anaesthesia between individual EEG recording channels. The intensities of activity flows were calculated for delta, theta, alpha and beta waves using the Directed Transfer Function integration procedure. It was found that delta waves played the dominant role in the EEG signal propagation during anesthesia and it was suggested that theta and alpha waves propagation could be related to the processes participating in the wakefulness control. Data obtained with DTF method were compared with data received from the analysis of cerebral blood flow with the use of PET in other laboratory. This study showed that analysis of the EEG signal propagation is useful for better understanding and thus safer induction of anaesthesia procedure.

Background Although electroencephalography (EEG)-based indices may show artifactual values, raw EEG signal is seldom used to monitor the depth of volatile induction of general anesthesia (VIGA). The current analysis aimed to identify whether bispectral index (BIS) variations reliably reflect the actual depth of general anesthesia during presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anesthesia. Methods Sixty patients receiving either VIGA with sevoflurane using increasing concentrations (group VIMA) or vital capacity (group VCRII) technique or intravenous single dose of propofol (group PROP) were included. Monitoring included facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, BIS, standard EEG, and hemodynamic parameters. Results In the PROP group no EPs were observed. During different stages of VIGA with sevoflurane in the VIMA and VCRII groups, presence of polyspikes and rhythmic polyspikes in patients’ EEGs resulted in artifactual BIS values indicating a false awareness/wakefulness from anesthesia, despite no concomitant change of FiAA, FeAA, and MAC of sevoflurane. Periodic epileptiform discharges did not result in aberrant BIS values. Conclusion Our results suggest that raw EEG correlate it with values of BIS, FiAA, FeAA, and MAC of sevoflurane during VIGA. It seems that because artifactual BIS values indicating false awareness/wakefulness as a result of presence of polyspikes and rhythmic polyspikes in patients’ EEGs may be misleading to an anesthesiologist, leading to unintentional administration of toxic concentration of sevoflurane in ventilation gas.

Background and Objectives: Raw electroencephalographic (EEG) signals are rarely used to monitor the depth of volatile induction of general anaesthesia (VIGA) with sevoflurane, even though EEG-based indices may show aberrant values. We aimed to identify whether response (RE) and state entropy (SE) variations reliably reflect the actual depth of general anaesthesia in the presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anaesthesia. Materials and Methods: A randomized, prospective clinical study was performed with 60 patients receiving VIGA using sevoflurane with the increasing concentrations (group VIMA) or the vital capacity (group VCRII) technique or an intravenous single dose of propofol (group PROP). Facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, RE and SE, and standard electroencephalographic evaluations were performed in these patients. Results: In contrast to periodic epileptiform discharges, erroneous SE and RE values in the patients’ EEGs were associated with the presence of polyspikes (PS) and rhythmic polyspikes (PSR), which were more likely to indicate toxic depth rather than false emergence from anaesthesia with no changes in the FiAA, FeAA, and MAC of sevoflurane. Conclusion: Calculated RE and SE values may be misleading during VIGA when EPs are present in patients’ EEGs. During VIGA with sevoflurane, we recommend monitoring raw EEG data in scientific studies to correlate it with potentially erroneous RE and SE values and the end-tidal concentration of sevoflurane in everyday clinical practice, when monitoring raw EEG is not available, because they can mislead anaesthesiologists to reduce sevoflurane levels in the ventilation gas and result in unintentional true emergence from anaesthesia. Further studies are required to investigate the behaviour of EEG-based indices during rapid changes in sevoflurane concentrations at different stages of VIGA and the influence of polyspikes and rhythmic polyspikes on the transformation of EEG signals into a digital form.